The Afghan government today blamed a Nato rocket in Helmand last week for the deaths of at least 45 civilians, including women and children. The allegation came as leaked US military intelligence reports revealed a large number of formerly unreported incidents in which innocent bystanders had been killed by operations involving foreign forces.

Despite strenuous recent efforts to stop such tragedies by restricting the freedom with which Nato soldiers can use lethal force, the latest incident happened on Friday as dozens of people from the village of Regey were hiding from nearby fighting between foreign forces and the Taliban, according to a government spokesman.

"The investigation shows that the rocket was fired by Nato and 45 civilians, many of them women and children, have been killed," Siyamak Herawi told Reuters. Some reports said the toll was as high as 52, including 17 women and seven children.

"Any speculation at this point of an alleged civilian casualty in Regey village is completely unfounded," he said. "We are conducting a thorough joint investigation with our Afghan partners and will report any and all findings when known."

The incident happened in Sangin, Helmand's most deadly district, from where British forces are soon to withdraw. It is not known which country's troops were involved in the nearby fighting, or who authorised the alleged missile attack.

Today, a spokesman for Nato confirmed that an operation against insurgents had taken place in the area, although an initial investigation had found no evidence of large numbers of innocent people being killed.

Strict new rules of engagement, which have been credited for the rapid fall in the number of civilian causalities caused by Nato, say heavy weaponry can only be used against a target when troops on the ground, overhead surveillance craft or trusted sources say there are no civilians present.

The issue of civilian casualties has been a source of great tension between the Afghan government and its foreign allies, with President Hamid Karzai getting into public slanging matches with the US.

The tighter rules on the use of force have angered some soldiers but been greatly appreciated by the Afghan government. Today, Karzai's spokesman made clear that the president appreciates the efforts made, and did not take the opportunity to condemn Nato for previously unreported civilian casualties revealed by Wikileaks.

These incidents included a possible war crime carried out in August 2007 when Polish troops fired a mortar at a wedding party in apparent revenge for a bomb attack on their unit. The mortar attack killed six people and the soldiers involved were put on trial in Poland.

But despite such harrowing examples of N attacks, Waheed Omar, the presidential spokesman, said considerable progress had been made in the last 18 months to reduce accidental killings.